There are technical and industrial needs for the efficient and economical production of single and arrays of small apertures. Particularly, the production of small apertures having a large aspect ratio (length (depth) of the aperture over the aperture size) can beneit a number of applications that use slits, masks, nozzles, collimators, filters and waveguides.
There is also a great need for apertures having a small aperture size (less than about 5 microns) with large aspect ratios. For example, these small apertures can provide high contrast masking and collimation necessary for high resolution detection by allowing an intense beam of radiation to illuminate a select area of a sample.
High quality, high aspect ratio apertures can also be used for waveguide applications where radiation bounces between the walls of an aperture. Waveguides greatly benefit from smooth, high-quality apertures and walls.
Ultra small apertures have a growing number of scientific applications as well. As an example, coherent X-ray diffraction (CXD) experiments can benefit from very small apertures having a large aspect ratio. In CXD experiments one must have an aperture to slit down (narrows) an X-ray beam to dimensions smaller than the transverse coherence length of the source, typically 5 microns or less.
There have been various efforts to efficiently produce high-quality apertures using methods such as mechanical machining, wire EDM (Electrical Discharge Machining), double blade precisely polished slits and laser drilling. Unfortunately, these methods have thus far proved unable to produce cost-effective high-quality apertures. Furthermore, none of these methods are capable of producing very small apertures with large aspect ratios. These traditional fabrication tools are currently unable to produce apertures much smaller than 5 microns, especially with a large aspect ratio.
Precisely polished double blade slits have had some success in generating apertures as small as a few microns, however calibration is difficult in these systems because controlling aperatures of about 1 micron or less requires precision stages and control that adds to the physical size and cost. The physical size of these systems makes them unrealistic to use in an array of apertures.
Laser drilling is another method of creating small apertures, typically as small as 5 microns. Pulsed high-energy solid-state laser and short-pulse deep ultraviolet (UV) laser have recently produced apertures as small as a few microns. Unfortunately, laser drilling produces irregular aperture shapes as a result of the laser ablation process and is thus far unable to produce apertures having lengths in excess of a few microns. Various lithographic techniques have also been used to produce small apertures, but in select metals, with limited aspect ratios and requiring specialized facilities and tools.
Therefore it is desirable to have a method to efficiently and economically produce one or an array of high quality small and ultra small apertures, especially with high aspect ratios.